Open parking under sun and rain,bantai cornering 100kmh,frequently polish/wax, can be the cause of hardening. Mileage how much on that tyre?

Sudah buat 15k km rotation?yes the warranty is 6 years but most of tyre at 30k-50k mileage can be consider at the end of their comfort/perform lifespan already. U can go more than 50k km if the thread still ok but u will get heavier cornering,lose grip,and roaring/bising tyre.